In a large bowl mix together ground beef and all the seasonings until well incorporated. Form (4) equal patties with the seasoned beef and grilled until desired doneness. Add cheese slices to each burger a minute or so prior to removing from grill. While burgers are cooking, slice focaccia bread according to burger size and lightly brush the inside with olive oil and grill until lightly browned. Prepare vegetables for topping burgers. Dress each burger on focaccia with lettuce, tomato and onion or according to taste.